The SN PLUS Service Category was introduced as a supplement to API SN specification in 2018 to mitigate low speed pre-ignition (LSPI) events in Turbocharged Gasoline Direct Injection (TGDI) engines. Such LSPI events can cause engine knocking, decreased efficiency, and in the worst case, catastrophic failure due to cracked pistons. As seen by the differences in the API SN and SN PLUS samples examined by PQIA over the past year, the SN PLUS formulations in the samples show lower calcium and higher magnesium levels than API SN. Whereas the average level of calcium in the API SN samples examined by PQIA is 2,060 ppm, the average of the SN PLUS samples examined to date is 1,217ppm. This represents a decrease of 41%. The average level of magnesium, however, has moved up to 691ppm, over 30 times above a negligible base of 22ppm. Calcium and magnesium sulfonate are the most commonly
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